1. Field of the Invention
The present invention relates to an injection apparatus, and more particularly to a disposable safety injection apparatus.
2. Description of the Related Art
As an injection apparatus such as a syringe has a substantial weight in the medical appliances. Particularly, some of the difficult-to-cure diseases including AIDS and various different types of hepatitis are spread in recent years, and thus infections caused by injections occur frequently and bring the attention of using medical appliances to people in different fields. As to syringes, using a safety disposable syringe with an autodisable function is a necessary and inevitable trend.
Basically, a traditional safety syringe includes a syringe needle, a liquid medication tube and a push rod. For example, a two-piece retractable safety syringe disclosed in R.O.C. Pat. No. 540385 issued on Jul. 1, 2003 includes a needle base disposed at a tube (or a liquid medication tube) for receiving the push rod, a lacerable slot disposed between the periphery of the needle base and the tube, a middle base disposed on the needle base and having a through hole, a latch member, and a push rod disposed at an end of the middle base and latched into the through hole, so as to constitute a safety syringe. After an end of the push rod is fixed to the needle base, the push rod retracts from the needle base and destroys the lacerable slot, such that the needle base fixed with a fixed syringe needle can be moved into the tube to prevent accidents or injuries caused by the exposed syringe needle.
The drawback of the aforementioned patent resides on that if the thickness of the lacerable slot is too large, say 0.12 mm, then the melted plastic liquid will flow into the gap to form a middle base with a through hole in the injection molding process. Since the groove is too thick and cannot be destroyed easily by external forces, and thus losing the autodisable function. If the thickness of the lacerable slot is too thin, say 0.06 mm, the lacerable slot can be destroyed easily by external forces, but the melted plastic liquid will not be able to pass through such a narrow slot, and the middle base with a through hole may not be formed integrally. Further, the lacerable slot at the top of the liquid medication tube comes with a weak design, and thus the needle base may be shaken by a torque produced by external forces during the injection or transportation process, or a leak may occur due to the crack of the lacerable slot.